


Undertale x Reader One Shots

by Yinsama



Category: Undertale (Video Game)
Genre: All the AU's, Alpha/Beta/Omega Dynamics, Angst and Fluff and Smut, Dom/sub, FTM Reader, Gender-Neutral Chara, Gender-Neutral Frisk, MTF reader, Mild S&M, Multi, Omega Reader, One Shot, Other Additional Tags to Be Added, POV Multiple, Reader remembers resets, Scientist Reader, Sex Magic, Shameless Smut, Sub Sans, Trans Male Character, alpha reader, and regular magic, beta reader, mafiatale, male reader - Freeform, mostly sans x readers, robot reader, so does flowey and frisk
Language: English
Status: In-Progress
Published: 2017-08-13
Updated: 2018-01-08
Packaged: 2018-12-10 21:33:38
Rating: Mature
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 9
Words: 3,667
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11700309
Author URL: https://archiveofourown.org/users/Yinsama/pseuds/Yinsama
Summary: Character x Reader one-shots. If a story needs a warning I'll note it before the start, smut warned with * in the chapter title. My updates will be at random. Prepare for cheesy titles. I will try to use a prompt for each one-shot





	1. New Masters Pt1

**Summary for the Chapter:**

> Prompt: "You don't know what I am, do you?"  
> Warnings: really vague, like you have to squint, brothels  
> Mafiatale-Robot! reader

"Master Frisk, what is it that you want?" The monotone robot asked; sighing as they re-tuck the blanket underneath the small child, the look in their eyes...they wanted something.

"How did you get here Miss Y/n?" Female was their chosen pronoun for them; depending on the certain master; he was a boy, or she was a girl or neither. Sometimes business called to be a different gender. 

"I walked into the room." They rise from their kneeling position smoothing over the crinkles in the plain dress shirt. Frisk huffs, dissatisfied with the robots answer. 

"No, how did you become a servant here?!" They ask, frustration causing their voice to raise in the slightest. Not bothered by Frisk's antics Y/n sat on the floor next to the bed, leaning against the frame. For a bit, the robot took false interest in the steady breath of the small human.  _You don't know what I am, do you?_

"Master Sans found me, broken and barely working. I was in the trash, broken by my previous master for scraps. My old master was a scientist and they wanted to customize the newest model, but they couldn't afford the parts they needed so they took what they needed from me. Useless, I was thrown away. I missed the parts that allowed me to walk, move my arms or my body. I could only make a soft clanking sound, even if I didn't want to, it was like the sound was on a loop. The sound caught Sans' attention from his post. He found me and took me to Alphys for repair. I was a gift to the company; robots are expensive and are illegal to monsters, the same goes for parts. As you know I now service the Dreemurr family and Company. I was renamed from my old master's original name for me to a more gender-neutral one, Y/n. " The robot finishes. 

"Is that why the family uses different pronouns for you?" They ask. 

"Yes. Miss Toriel uses she and her, Papyrus and Mettaton uses them, Alphys and Asgore also uses female pronouns. Sans and Undyne use male pronouns," Finishing, the android lets the silence fall."You should go to sleep now." Patting their head, Y/n leaves, closing the door behind them.  

"what a lie ya' to pup there." There stands the stout skeleton named, Sans. 

"They're too young to know what really happened." The robot walks down the hall, dress shoes clipping against the wooden floor. Yes, Sans did save them from being destroyed, was the action more deliberate and deadly? Yes. Were they really a service bot? Sort of if you could consider that kind of work service. Y/n held too much valuable information to be allowed that kind of work. 


	2. Socially Acceptable

**Notes for the Chapter:**

> Prompt: "I'm not supposed to express my emotions! I'm a boy!"   
> Underswap sans x Male reader  
> tags: body conscious reader, self-conscious, platonic or romantic, comfort
> 
> probably do another with a different body type and or issue

You look at yourself in the body mirror. You're bare from the waist up, the only clothing is your baggy jeans and a tightly wrapped belt. God, was skinny the right word to describe you? No matter what you ate, whether it be Muffets sweets or Sans's taco's, you couldn't build up muscle mass or any mass at all. Stick thin, tall, and honorary skeleton bro is good adjectives. Alphys was your hero, even though you were a good one and a half foot taller than her, she was meaner and beefier than you could ever dream to be. Sence making peace with the underground you started training along side Sans; god was he fast. Being human your were resilient to attacks, but you were rather average when it came to attacking and dodging.  

You ran a hand across your pecs and the faint outline of what could be abs. A sigh escapes your lips;  _boys don't think about their looks, that's for girls...pussy._ You weren't known for dark thoughts and outlooks. You were a rather nice guy, nick-named the boy next door by Dr. Udyne. But you despised how you looked then you would criticise the fact it wasn't socially acceptable for you to act this way. Your body made you uncomfortable then your self-esteem would drop and you would feel the need to cry.  _Boy's don't cry...but Sans cry's openly and he's a boy._ "Agh!" You growl out conflicted. You were raised to be tough, but the underground was so...emotional and open. Your anger and sadness bubbled up to the point and you did the one thing you knew. You punched the mirror. 

Maybe that wasn't the best idea, but it was the only outlet you knew. Your hand lay limp in the air, jagged pieces of glass stick out from the spaces of your knuckles. The pain hits you as you tug on a shard allowing beads of blood to drip between glass and skin. Within a minute or so Sans rushes in. "I heard a smashing sound are yo-" he cuts off, taking notice of your dull stare at your hand, or maybe he noticed the smashed mirror reflecting broken and distorted images of the room and them. "Y/n." You look at him, before returning to tugging the small shard. "No, let me." Sans crosses the room to you, pushing you onto your bed and grabs your hand. "I don't know why you did this but I can take a guess." He speaks as he pulls out the glass; you hiss and he mutters a quick apology. "I know you don't like your body, but your fine the way you are and whatever anyone says...it's a bunch a boo hockey anyway." Your mouth tugs upwards a bit, that's about as closes as Sans will get to cursing.  

"It's not just that. It's here I guess; people are so open with their emotions and theirs me and I want to but I don't want to or I can't...You don't know what I mean." You mutter.

"It's okay to be sad no one will judge you!" Sans looks at you with a smile.

"That's the thing, I'm not supposed to express my emotions! I'm a boy!" You raise your voice slightly. 

"I don't know what it was like up there for you Y/n, but just know that your gender defines nothing of who you are. What defines you is you. No one can take that from you." Sans removes the last piece of glass, " Here you can be whatever you want to be. Just promise me you'll try." 

You rest your forehead against him. "I won't make any promises. Can't promise I'll get better soon, but I'll try." You whisper, fatigue from your outburst setting in. 

"Mweh heh! That's all I wanted." 

 


	3. New Masters Pt2

**Notes for the Chapter:**

> tags: sex-bots, genderfluid reader

Y/n held a lot of information. They were a bartender and occasionally a service bot at a local brothel. The robot always collected data on what patrons did so it wasn't a surprise when Y/n knew all about a gangs certain "client". Originally Undyne was sent in to collect information but couldn't get a peep from the secretive robot. 

"I will smash your face in!" The large fish threatened.  

Acting on not self-preservation but protocol the bot responds, "You won't get information out of me if you destroy me."

"NGHH!" Undyne growls out.  

"I'm going to have to ask you to leave." Undyne leaves. 

A week passes with no incidents until the boss gets's a new worker. The female bot was shorter than Y/n, bustier, more feminine too. But it didn't have one thing; pre planned protocol. They dismantled Y/n for spare parts and their data. Soon Y/n was tossed out, useless to anyone. Sans was walking to the brothel, his turn to try to get information, being cooler at handling these types of situations then Undyne. As he walked near the alleyway next to the brothel he heard a clipping noise. Like a cd scratched, repeating a certain sound over and over again. Sans looks into the alleyway seeing a lewdly dressed service bot, broken down and hissing static. 

"y'er the robot undyne was takin about aye?" The bot couldn't respond but didn't stop the clipping noise. "welp i hope you still have some information on ya." What he was doing was highly illegal. A monster taking a bot was restricted everywhere getting caught with one in possession could get him killed. So Sans picked up the surprisingly light frame and teleported the robot and him to the back of Grillby's or also known as the entrance to the base. 

Luckily enough even though they lost all stored data in their chip, almost all of the gang's clients whereabouts were stated to the bot and saved on a camera installed on the bot.After being repaired the bot was renamed, redressed and re-serviced.  

Now a servant to a monster mafia gang, Y/n goes out to collect data from unwilling clients and picks up Frisk from school. 


	4. Authors note

chapters bound to come: 

~~**body type reader pt 2** ~~

~~Underfell-muscular female reader whose tall with broad shoulders~~ (chapter completed) 

 

**seven deadly souls series ( seven chapters )**

Seven chapters dedicated to the reader having a certain core trait, but each trait comes with a power or flaw. ex: blind justice comes to mind easily. I'm not so certain about the others so give me ideas.   

~~**Mafia robot pt 3** ~~

~~Maybe the reader get's a virus or Alphys gives them emotions for the first time.~~

**Mafia robot spin-off (based on the song I know I'm a wolf.)**

A concept I have been playing with. The reader leaves the Mafiatale timeline for a more stable place, Underswap, and tries to earn the trust of the two brothers mostly Papyrus. This would be after the reader gets the ability to emote so there might/will be some swap sans x reader.

**A/B/O dynamics**

Three chapter dedicated to the reader being an alpha, beta or an omega. Two out of three will be smut. 


	5. A Bastard

**Summary for the Chapter:**

> A poor reader takes in two homeless monsters with a rare act of kindness.

**Notes for the Chapter:**

> Child Sans and Papyrus x Theif!Reader

You are not really certain why you decided to bring the two skeleton's home, but you did. You chalked it up to not wanting them to live like you used to, still do. That's not the full reason...maybe since you saw tons of kids on the streets, and rarely helped them; you yourself were only a teen and could barely take care of yourself. Yet here you were with two small monsters under your charge. The skeletons were brothers you found huddled unconscious in a dumpster in your ally. In a move of rash decision-making, you took the home. The smallest one, who you would later learn was Sans, fought you tooth and nail. You understood but made your statement clear: I'm keeping you two safe, don't fight. You offered him food, a couple slices of bread, which he took to his brother in the spare bedroom of your rather small house. You offered him some more bread, which he ate himself.     

This continued for a few months and soon when you learned their ages, 10 and 8, you had them go to school. Of course not a public one, too expensive. You knew an old lady who taught the poor and homeless children how to read and write, basic math too. You used to go there before you became pressed for money; now you work and sometimes steal when times are tough. You weren't surprised though when Sans' asked you that question, he was a smart kid, as you were walking back home from the market. "why don't you go to school, y/n?"  

"I have a job, don't have time for school, no more." You respond. You shifted the few bags on your arm to a more comfortable place on your elbow.  

"then how old are you?" He asks again. You chuckle;  _why does he worry?_

"That's not important bucko." You dodge the question. 

"then why dodge my question?"  _Fuuuuck._

"Sans it's none of your worries about how old I am, you should worry more about your homework." He frowns at you, odd for his usual smiley deminer. 

"just tell me already, please y/n." You sigh. 

"I'm 15 Sans, happy?" You turn with him into your ally which leads to your small house. 

"not really." Sans states. 

"Then why ask." It didn't quite come out as a question. 

"because you always take care of us, with no reason to. but who takes care of you y/n?" Entering the house you set the few bags down on the table and turn back to Sans. Papyrus should be with Nana still, you'll need to pick him up soon. "you think we don't notice, papyrus doesn't but i do. i see you come home late at night limping covered with bruises and blood and i'm not sure if it's yours or not sometimes. or the sudden influx of money near our birthdays and holidays, but never your birthday. i know i have no right to ask, but what happened to get you here?" You see so much pain in his eyes as he looks up at you, that you sigh as you sit in one of the wooden chairs.  

"Sans' I was a bastard born from a whore and man too rich to care about a slut he knocked up. For ten years I was raised in a brothel until my mom died from pneumonia caused by AIDs. I have done some things that I'm not so proud of to get where we are now. Don't for the love God let how I was raised effect how you and Papyrus grow up, cause I swear on my life that you two will get it better than me if it's the last thing I do. Don't worry about me, you have nothing to worry about." You stand up. "Do your homework, Sans. I have to pick up your brother." You leave. 

Sans and Papyrus didn't have the greatest start, abandoned at a young age, Sans had to do some minor stealing if he wanted food and clothes for his brother and him. He understood were Y/n came from. And he was happy he didn't have to worry when the next meal came from, he still did though, leaving conditions wasn't the best but it was better than the dumpster he was found in. Sans just hope that Y/n and Papyrus and him, will end up somewhere better like Y/n said, but for now, this was okay. 


	6. Socially Acceptable 2

**Notes for the Chapter:**

> female masculine reader   
> Underfell sans x reader

"Goddamn Boss, with Undyne's training I can't wait for you to take over!" You laugh as you arch your back to release some tension in your lower back. Papyrus snorts at you as he locks the front door.  

"Don't worry human, when I am the Captian of the royal guard, training will be a whole lot tougher!" 

"Don't make me regret my praise Boss." You respond. Sometimes you like to think back on how you got here. Sans falling for you and you him, proving your moxy to Papyrus by almost killing him, befriending Undyne and Asgore. Asgore the king of monsters, horrid in his ways, cold in his profession. You call him King Fluffybuns to piss him off but you think he likes it secretly. 

"hey, sweetheart." Sans walks down the stairs to the couch where the two of you were at.

"Hey." You smile. You weren't one for pet names, but Sans made up for that will his almost endless list of them. Since no one outside could see you three, you could act as you please, so Sans decides to hug you. You always found this cute; Sans would stand on his tippy toes to wrap his arms around your neck. You rest your arms at his waist and nuzzle his temple. You always wondered how tall he was, you assumed maybe 5ft at best. Picking Sans up you plop onto the couch, not bothering to turn on the tv, knowing all that will be own is Mettaton and you weren't in the mood for gore today.  

Letting your thoughts wander as the soft clatter of Papyrus cooking dinner and Sans gentle purring as you pet his skull, lulls you into a daze. Oddly enough being here in this violent world, stops thoughts that were outside of self-preservation. Most of the time you thought about the need for money or protection, safety for Sans and his brother, yourself; but in these moments of calm when everything was okay, your brain became conscious of your body. You couldn't help it, before falling you were raised to be pretty and proper since you were a girl, but you were just too tall, your shoulders too broad. Plus since your fall you have become tougher, stronger, you built muscle mass. Your hair was decent in length, short enough to be convent to your violent lifestyle but long enough for Sans to play with.You've heard of Sans other "toys." You bet they were all short and curvy. You sometimes wonder why he likes you. 

"stop thinking about that y/n" Sans roughly pulls your face down to him. " your such a fucking hypocrite ya' know? you think and talk so negatively about your body yet you date a fucking skeleton. a skeleton for christ sakes!" You chuckle, Sans was alway good at reading people. 

You smile softly. "Fuck you too Sans."  Sans gets a shit-eating grin and wraps his hands into your hair.     

"maybe later, sweetheart."    


	7. New Masters "I have the flu"

"is he sick?" Sans asks the good doctor or Alphys. 

"W-well technically a-a robot can't get sick l-like monsters or humans since they have no soul." 

"so..what is it then? malware, system malfunction... " Sans drags on. 

"A virus." Alphys responds. You assumed that was the right thing. You were out of it; your systems were heating up and crashing. You had problems moving and speaking or seeing..or really anything. You could compare this to the flu or fever. "Well I-I can easily c-cure this, it'll al-also gives m-me the chance to test out my new upgrade." 

"what do ya' mean doc?" Sans leans against the bed your sitting on. Alphys moves to her desk and digs around in a cabinet before pulling out an integrated circuit. 

"This would program Y/n to understand emotions." Alphys stops stuttering as she gets more technical. "Their body will shut down so they can sort the data they have collected into emotions. Though this could cause some problems as they might think more with their 'heart' then their logic. On the other hand, it would give them a personality." 

Sans looks at you. Do you want emotions? You have no idea you never had a real desire before so you'll leave this up to Sans. "You make the choice master Sans." You nod your head to him. The skeleton scratches his head. 

"do it doc, what ever happens is for the best." He gives your metal hand a squeeze before leaving the lab. 

"Okay, Sans, I'll let you know when they've booted back up," She turns to you and has you bend your head down, "I hope this works well." 

Your system reads the chip, you except it and your system shuts down to update its self.

 

The Dreemurr home will forever be different.  

**Notes for the Chapter:**

> after this, i think i'll do two more chapters   
> one being an alternate ending to masters where the reader realizes their lifestyle hates it and finds a way out of this timeline and into the underswap timeline
> 
> the second one being the reader falling in love with someone (probably sans) 
> 
> after that, i might start sexualizing the reader (put a whole new meaning to mAsTERs-oh!)


	8. you take care of yourself, cause someone really cares about you

**Notes for the Chapter:**

> angst maybe it's not too sad i think, but does deal with a sensitive subject. 
> 
> Warning: drug over-dose, vent

There was a mixture of anger and sadness in the their eyes. Their voice was calm if not dead and cold in tone. “You’re going to overdose.” The room was dark except for the light that emitted from the bathroom. Sans sat on the edge of the bed, eyes casted down. It was pointless they thought, he’s drugged himself, probably too out of it to listen. “How long Sans…” They pause, sighing, nothing was working, “since you’ve been doing this? Ten years, fourteen?”

“I don’t know.” His voice was soft and his body swayed a bit.

“You don’t know.” They trail. They bite their lip; god they cared for him so much, he said he loved them as well, but old habits die hard. They lay Sans down, he’ll be fine they just have to keep an eye on him for the night. Sans falls asleep quickly as expected, while Y/n digs around everywhere; shelves, the nightstand, under the bed, closet and trash tornado, and ends up confiscating three bottles of 50mlg of melatonin; a sleeping aid.

Things won’t get better soon, not for awhile, but this was a start.

**Notes for the Chapter:**

> the backstory behind this was based on my confrontation with a friend at their house. they swallowed five 50mlg pills of melatonin and dropped and shattered a glass.


	9. Reaper!Reader x Genocide Sans

**Notes for the Chapter:**

> warnings: genocide spoilers, character death  
> prompt: "does it ever stop hurting?" "No you just make room for it."

Your bare feet touch the gold tile, moving forward with almost no sound. Sans looks up, a red liquid dripping from the bottom of his mandible and seeps through a rip across his shirt. He makes eye contact with you. 

You. Death. The Grim Reaper. The one who makes death cold. 

"are y-you real?" He chokes a bit in the middle. 

"As real as you think I am." Your voice slow and tired. You leaned your weight to your side, adjusting your scythe a bit. " Sans of Snowdin, age 23, male, only known relatives is your brother Papyrus who is deceased. He was a nice man." You draw back to when you were reaping him, such a sweet soul, he'll find happiness with the Goddess of Life Toriel. 

"why are you telling me this?" Sans can no longer support his weight and falls to his knees catching himself with his palms. 

"Sans you need to let go." Your voice turns maternal in hopes of letting him relax and dust. 

"will...will..." He pauses, "does it ever stop hurting?" You bow to one knee and extend your hand. 

"No, you just make room for it." He looks at you and his shoulders slump. He takes your hand and you smile softly at him. "Good. Now we better get going, someone is waiting for you." As he dusts the room fades out to white and all that is left is you, him, and a figure in the distance. 

"You better go, Sans, can't keep him waiting." The small skeleton looked better without the rip going through his shirt. Sans grin looked peaceful and his eyelights brighter as he looked at you. 

"thanks."


End file.
